1. Field of the Invention
The present invention relates to a polishing pad suitable for chemical mechanical polishing (CMP), a polishing apparatus having the same, and a bonding apparatus.
2. Description of the Related Art
Conventionally, a semiconductor integrated circuit has been formed by depositing insulating layers, conductive layers, and so forth on a silicon wafer. Each layer is etched during the formation processes. As a result, steps are formed in each layer. With such steps, even the same layer has a highly conductive portion and a low conductive portion, so that a desired electrical characteristic cannot be obtained. Therefore, planarization by CMP is performed after etching when necessary.
For performing CMP, a polishing pad is bonded to a CMP apparatus. Polishing pads in various shapes are available, and for example, those having grooves arranged along the circumference, those having grooves arranged in grid pattern, and so on are available.
FIG. 6A and FIG. 6B are schematic views showing an example of a conventional polishing pad (first conventional example). Note that FIG. 6B shows a cross section taken along the I—I line in FIG. 6A. The first conventional example, which has a double-layer structure, is composed of a base member 101 to be bonded to a surface plate 10 and a polishing member 102 having irregularities formed on a front surface thereof. On the polishing member 102, a plurality of projections 102b and grooves 102a are formed. The grooves 102a are formed in grid pattern, each having a rectangular cross section. Ends of each of the grooves 102a extend to the outside of the polishing member 102 to allow slurry and the like entering the inside of the grooves 102a to flow outside. A polishing portion 103 covers the entire polishing pad in a plane view.
The first conventional example as described above, however, has a problem of poor bondability to the surface plate 10. This is because the grooves 102a are formed on the entire polishing pad, and portions in which the grooves 102a are formed in particular are poor in bondability. Consequently, small gaps are formed between the portions in which the grooves 102a are formed and the surface plate 10, and the slurry and the like enter the gaps. If the slurry and the like enter, adhesive strength further lowers, sometimes resulting in peeling of the polishing pad off the surface plate 10 during the polishing. This sometimes causes in the worst case the breakage of a silicon wafer. Another problem is that abrasive and the like contained in the slurry remain on the surface plate 10 when the polishing pad is peeled off after the polishing is finished. The residual abrasive and the like will obstruct ensuring high planarity when the polishing pad is bonded the next time, so that a wafer cannot be sufficiently planarized.
Therefore, a polishing pad with improved bondability has been proposed. FIG. 7A and FIG. 7B are schematic views showing another example of a conventional polishing pad (second conventional example). Note that FIG. 7B shows a cross section taken along the I—I line in FIG. 7A. In the second conventional example, a wall portion 104 is formed around a polishing portion 103. Further, grooves 102b have the same depth in a center portion but in areas close to the wall portion 104, the grooves 102b closer to the wall portion 104 have shallower depth.
According to the second conventional example as described above, since it is possible to inhibit the deterioration of bondability of the portions in which the shallow grooves 102a are formed, the aforesaid peeling and entering of slurry and the like can be inhibited. However, the existence of the wall portion 104 outside the grooves 102a makes it difficult to discharge the slurry and the like that have entered the inside of the grooves 102a. Consequently, an excessive amount of the slurry and the like may possibly stay in the polishing portion 103, which sometimes causes a scratch and the like on a wafer during the polishing.
A related art is described in Japanese Patent Application Laid-open No. 10-71561.